A bomber strikes outside a mosque in an opposition stronghold of Damascus, the Syrian capital. Bashar Assad's government blames terrorists, but the opposition accuses the government.

Syrian investigators are seen through a police bus window that was damaged… (Bassem Tellawi, Associated…)

BEIRUT — Two weeks after a supposed cease-fire was meant to bring an end to violence in Syria, an explosion Friday ripped through the capital, Damascus, killing at least nine people and injuring almost 30.

A suicide bomber in the pro-opposition Midan neighborhood detonated an explosives belt near a school and the Zein Abidin mosque as worshipers were leaving Friday prayers, the Interior Ministry said. Those killed included civilians and law enforcement officers, state media said.

The ministry blamed "terrorist groups" for the attack, but opposition activists said the government was probably behind the blast.

The bombing came two days after an explosion in the central city of Hama razed several homes and caused numerous deaths. Activists and the regime traded accusations in that attack as well.

The attacks mark a further crumbling of the United Nations-backed cease-fire announced this month, meant to start the implementation of a six-point peace plan to end 13 months of violence and unrest.

Since the cease-fire announcement, the bloodshed has escalated as President Bashar Assad's government continued its crackdown on the opposition. The rebel fighters, who had agreed to the cease-fire, have reportedly taken up arms again.

Moaz, a Damascus activist who asked to be identified by only one name for security reasons, rejected the government's claim that the bombing was the work of antigovernment forces, pointing out that Midan is an opposition stronghold. The mosque near the attack also has been a focal point for demonstrations, Moaz said.

"In Midan on Friday, the security forces are stationed in every mosque and the eyes of the security are on the neighborhood," he said in an interview using the Skype communications system. "So how does an explosion like this happen?"

The explosion prevented protests in Midan on Friday. But elsewhere in the country, throngs of protesters took to the streets, demanding the ouster of Assad.

Activists said government troops opened fire on demonstrations in several areas, including the towns of Dair Alzour, Taseel and the Zahira neighborhood of Damascus. Eleven people were killed and dozens injured, according to activists.

Unlike last week — when U.N. monitors said they would not be out on the streets on Fridays, in a decision that was heavily criticized by opposition activists — the observers visited several volatile areas.

Four monitors were splitting duty in the cities of Homs and Hama, and two others were sent to the southern province of Dara, said Neeraj Singh, a spokesman for the observers. The team of observers stationed in Damascus spent Friday visiting Hama and the northwestern province of Idlib.

"The military observers are all out in the field," Singh said in an email. "They are maintaining presence in their respective areas and carrying out their activities."

On Friday,U.N. Secretary-General Ban Ki-moonannounced the appointment of Maj. Gen. Robert Mood of Norway to head the monitoring mission in Syria. The Security Council last week authorized 300 monitors, with the first 100 to be deployed within a month.

So far there are 15 monitors in the country, with another 15 expected to arrive by Monday.